A base station of a radio cellular telecommunications system is connected to one or more amplifier assemblies via which the base station receives signals from and transmits signals (from the network) to mobile units within the range of the base station. Many such antenna assemblies will include (in the antenna radome) phase shifters for altering the antenna beam tilt. Due to handset power and battery life restrictions on the mobile units, the signals received from the mobile units can be of a very low intensity. In previous generations of cellular mobile telephone systems, mast head amplifiers were occasionally required in order to boost the signals received by the antennas.
However, during the deployment of the current 3G UMTS telecommunications system it has become apparent that an amplifier is required at each antenna. A mast head amplifier needs to include various high frequency filters which take the form of filter cavities. As a result, mast head amplifiers tend to be relatively large metal objects, which, if placed too close to the radiating elements of the antenna arrays, could cause pattern interference.
Consequently, a mast head amplifier is conventionally mounted in a position spaced from the radome which contains the radiating elements of the antenna. Thus the mast head amplifier needs to be provided with its own weather proofing, and therefore considerably adds to the size and cost of the mast head amplifier and antenna assembly. In addition, the increased size of the assembly can lead to possible problems in obtaining planning permission for erecting the apparatus.
Furthermore, the loses associated with the cabling used to connect the mast head amplifier to the antenna radome and the radome ports to be the phase shifter can degrade the received signal.